Such an assembly is known according to which the traction vehicle, of the type with motor tracks and steered by a person behind the vehicle, comprises a fixed rigid arm protruding in front of the vehicle and at the end of which is freely suspended the soil treatment machine which can move, while remaining in contact on the ground by its own weight, in the forward direction by the thrust exerted by the traction vehicle on the soil treatment machine.
The suspension of the soil treatment machine at the end of the support arm is done via a connecting mechanism allowing the machine to move vertically in relation to the support arm so that it follows the height differences of the soil, due to unevenness thereof.
This connecting mechanism is formed by at least one pair of articulated connecting rods of the same length constituting a deformable parallelogram thereby allowing the machine to be raised or lowered vertically in relation to the support arm during movement of the machine on irregular ground.
FIG. 1 diagrammatically illustrates a deformable parallelogram with sides parallel in two pairs A, C and B, D, whereof the two small parallel sides B, D respectively constitute the two connecting rods hingedly connected by their ends in 1C, 2C and 1A, 2A to the support arm of the traction vehicle and to the hood of the soil treatment machine. In this figure, the soil treatment machine occupies a low position in relation to the fixed support arm. This parallelogram deforms while remaining open above the axis X-X′ passing through the lower articulations 1A, 2A of the connecting rods B, D to the hood of the soil treatment machine for corresponding amplitudes of vertical displacement of the machine relative to the support arm.
FIG. 2 shows the situation according to which the parallelogram is closed during a determined amplitude of the upward movement of the machine relative to the support arm, i.e. the two connecting rods B, D are essentially aligned along the axis X-X′ called closing axis of the parallelogram.
When the soil treatment machine moves further upward relative to the arm of the traction vehicle, because the sums of the two adjacent sides A, B and C, D of the parallelogram are equal, the parallelogram is broken, i.e. the two connecting rods B and D are no longer parallel due to the fact that the pivoting of the articulation point 1C of the connecting rod B around the articulation point 1A below the closing line X-X′ causes the articulation point 2C of the connecting rod D to rise around the articulation point 2A as illustrated in FIG. 3. In the position illustrated in FIG. 3, the two connecting rods B and D block any additional upward movement by the treatment machine relative to the support arm, able to cause breaking of the articulations of the connecting rods and when the soil treatment machine again lowers in relation to the support arm from the position illustrated in FIG. 3, the pivoting of the connecting rods B, D toward the closing line X-X′ passes by a hard spot once again risking breaking the articulations of the connecting rods.
Thus, the mechanism with two articulated connecting rods making it possible to suspend the soil treatment machine from the support arm of the traction vehicle limits the displacement height of the treatment machine relative to the support arm according to the irregularities of the soil, unless one provides longer connecting rods, to the detriment of the compactness of the assembly formed by the machine and the support arm. Moreover, the suspension mechanism of the connecting rods does not ensure good vertical guiding of the machine relative to the support arm.